The present invention relates to a turbocharger for use in an internal combustion engine, and, more particularly, to a turbocharger having a two-stage compressor.
An internal combustion engine may include one or more turbochargers for compressing a fluid which is supplied to one or more combustion chambers within corresponding combustion cylinders. Each turbocharger typically includes a turbine driven by exhaust gases of the engine and a compressor which is driven by the turbine. The compressor receives the fluid to be compressed and supplies the fluid to the combustion chamber. The fluid which is compressed by the compressor may be in the form of combustion air or a fuel and air mixture.
A turbocharger may also include a two-stage compressor with two separate compressor wheels which are carried and driven by a common shaft coupled with the turbine. U.S. Pat. No. 5,157,924 (Sudmanns) discloses a two-stage compressor with compressor wheels which are carried by a common shaft and disposed in a face-to-face manner relative to each other. The two compressors are arranged in a parallel manner such that each compressor provides an output to a charge air collecting duct in parallel. During idle or light load conditions during operation, the outlet of one of the compressors is closed so that only a single compressor provides an output to the charge air collecting duct.
With a two-stage compressor as disclosed in Sudmanns ""924, the pressure ratio on the output side of the two compressors is limited since the compressors provide an output in a parallel manner to the charge air collecting duct. Moreover, stalling one of the compressors by merely closing the output therefrom may result in overheating of the compressor.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the invention, a turbocharger for an internal combustion engine is provided with a rotatable shaft. A first compressor stage includes a first compressor wheel carried by the shaft, an axially extending first inlet and a radially extending first outlet. A second compressor stage includes a second compressor wheel carried by the shaft, an axially extending second inlet and a radially extending second outlet. An interstage duct fluidly connects in series the first outlet of the first compressor stage with the second inlet of the second compressor stage. The interstage duct includes a bypass opening in communication with an ambient environment. A valve is positioned within the interstage duct. The valve is moveable to and between a first position to close the interstage duct and a second position to close the bypass opening.
In another aspect of the invention, an internal combustion engine is provided with an intake manifold and a turbocharger. The turbocharger includes a rotatable shaft. A first compressor stage includes a first compressor wheel carried by the shaft, an axially extending first inlet and a radially extending first outlet. A second compressor stage includes a second compressor wheel carried by the shaft, an axially extending second inlet and a radially extending second outlet in communication with the intake manifold. An interstage duct fluidly connects in series the first outlet of the first compressor stage with the second inlet of the second compressor stage. The interstage duct includes a bypass opening in communication with an ambient environment. A valve positioned within the interstage duct is moveable to and between a first position to close the interstage duct and a second position to close the bypass opening.
In yet another aspect of the invention, a method of operating a turbocharger in an internal combustion engine is provided with the steps of: providing a first compressor stage including a first compressor wheel carried by a shaft, and axially extending first inlet and a radially extending first outlet; providing a second compressor stage including a second compressor wheel carried by the shaft, an axially extending second inlet and a radially extending second outlet; fluidly interconnecting in series the first outlet of the first compressor stage with the second inlet of the second compressor stage with an interstage duct, the interstage duct including a bypass opening in communication with an ambient environment; positioning a valve within the interstage duct; moving the valve to a selected position between a first position closing the interstage duct and a second position closing a bypass opening; and rotating the shaft with the first compressor wheel and the second compressor wheel.